T-Mobile and AT&T customers in the impact zone of Hurricane Sandy will share cellular networks through a mutual aid pact announced today by both companies.

The temporary roaming agreement will allow customers of AT&T and T-Mobile to use cell sites providing the strongest reception and the highest call completion rate in areas of New York and New Jersey where cell service has degraded.

T-Mobile said the temporary arrangement will provide a seamless roaming experience because both companies share GSM technology. There will be no additional charges for this service. We have no information as to whether this agreement will also cover texting and data services.

Earlier today, T-Mobile provided this update to customers about restoration progress:

T-Mobile network engineers are working as quickly as possible to restore service to areas affected by Hurricane Sandy. In Washington, D.C. the network is more than 90% operational. In New York City, the network is more than 80% operational. Restoration work continues in the harder hit areas of lower Manhattan, Staten Island, Long Island, coastal and Northern New Jersey, Connecticut and portions of Pennsylvania, including Philadelphia.

T-Mobile rapid response engineering teams have staged equipment throughout the areas most severely impacted and continue to make assessments regarding how quickly we may be able to begin restoration, and where it is needed most.